Evidence

DISCLAIMER:
These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.

Asthma:
Research has shown caffeine to cause improvements in airflow to the lungs (bronchodilation). However, it is not clear if caffeine or tea use has significant clinical benefits in people with asthma. Better research is needed in this area before a conclusion can be drawn.
Grade: C

Cancer prevention:
Several studies have explored a possible association between regular consumption of black tea and rates of cancer in populations. This research has yielded conflicting results, with some studies suggesting benefits, and others reporting no effects. Laboratory and animal studies report that components of tea, such as polyphenols, have antioxidant properties and effects against tumors. However, effects in humans remain unclear, and these components may be more common in green tea rather than in black tea.
Some animal and laboratory research suggests that components of black tea may be carcinogenic, although effects in humans are not clear. Overall, the relationship of black tea consumption and human cancer remains undetermined.
Grade: C

Colorectal cancer:
Although there is strong evidence from animal and laboratory studies that black tea may help prevent colon cancer, human studies are limited. Additional research is needed.
Grade: C

Dental cavity prevention:
There is limited study of black tea as a mouthwash for the prevention of dental cavities (caries) or plaque. It is not clear if this is a beneficial therapy.
Grade: C

Heart attack prevention / cardiovascular risk:
There is conflicting evidence from a small number of studies examining the relationship of tea intake with the risk of heart attack. Tea may reduce the risk of platelet aggregation or endothelial dysfunction, proposed to be beneficial against blocked arteries in the heart. The long-term effects of tea consumption on cardiovascular risk factors, such as cholesterol levels and atherosclerosis, are not fully understood.
Other research suggests that drinking black tea regularly does not affect plasma homocysteine levels or blood pressure. Black tea may increase heart rate.
Grade: C

Memory enhancement:
Several preliminary studies have examined the effects of caffeine, tea, or coffee use on short and long-term memory. It remains unclear if tea is beneficial for this use.
Grade: C

Mental performance/alertness:
Limited, low-quality research reports that the use of black tea may improve cognition and sense of alertness. Black tea contains caffeine, which is a stimulant.
Grade: C

Methicillin-resistant Staphylococcus aureus (MRSA) infection:
In one small study, inhaled tea catechin was reported as temporarily effective in the reduction of MRSA and shortening of hospitalization in elderly patients with MRSA-infected sputum. Additional research is needed to further explore these results.
Grade: C

Oral leukoplakia/ carcinoma:
Early studies report that black tea may lead to clinical improvement in oral leukoplakia and therefore prevent oral carcinoma. Further research is needed to confirm these results.
Grade: C

Osteoporosis prevention:
Preliminary research suggests that chronic use of black tea may improve bone mineral density (BMD) in older women. Better research is needed in this area before a conclusion can be drawn.
Grade: C

Stress:
Based on early research, black tea may reduce stress and help patients feel more relaxed. More research is needed to confirm these findings. It should be noted that high doses of caffeine have been linked to anxiety.
Grade: C

Weight loss:
Black tea has been used as part of a combination supplement to help patients lose weight. Although patients in the study lost weight, the effects of black tea alone are unclear.
Grade: C